1. Field of the invention
The present invention relates to an inkjet print head and a method of manufacturing the same.
2. Description of Related Art
Inkjet print heads are widely used in various industrial fields since they can produce print at a relatively lower cost than a laser printer. They also can provide higher resolution than dot-matrix printers. For example, an inkjet print head is used to print a color filter layer of a liquid crystal display device.
However, since an inkjet print head uses a liquid ink, the liquid ink may become easily blurred on the printing paper or the printing plate and nozzles of the print head may become blocked because of the dregs in the liquid ink.
FIG. 1 shows a conventional inkjet print head. The print head 10 moves back and forth or right and left and sprays ink through nozzles 12 to print desired lines or data. However, since the print head 10 of the inkjet print uses a liquid ink, dregs of the liquid ink may remain inside the nozzle 12.
FIG. 2 shows a configuration of the print head. As shown in FIG. 2, the print head comprises an ink pool 14, a plurality of screens 16, and a piezo element 18. The ink pool 14 holds the printing ink, and the screens 16 are arranged between the ink pool 14 and the piezo element 18. The piezo element 18 serves to pump the printing ink from the ink pool 14 to the nozzle 12 through a channel 20 according to a predetermined controlling signal from the external drive circuit (not shown). The piezo element 18 further serves to forward the printing ink to a direction of an arrow xe2x80x9caxe2x80x9d. At this time, a lower portion of the piezo element 18 secures a big area enough to provide the piezo element 18 with a working space. Further, the channel 20 is connected with the lower portion of the piezo element 18 and becomes narrow in a direction away from the piezo element 18.
The screens 16 are formed on a wafer or a glass substrate 1, as shown in FIG. 3, and have a convex-gully shape. A concave portion between the screens 16 is a portion that is etched. The screens 16 serve to regulate the flow of the printing ink so that an excessive amount of the printing ink is not supplied from the ink pool 14 to the piezo element 18. Accordingly, a pumping energy of the piezo element 18 is uniformly provided to the nozzle 12, so that an appropriate amount of the printing ink is sprayed.
In the mean while, as shown in FIGS. 4A and 4B, since the nozzle 12 of the print head has a high hydrophilicity, i.e., a high water affinity as described above, dregs 24 of the printing ink 22 collect inside the nozzle 12, eventually clogging the nozzle 12. In addition, the nozzle 12 may be suddenly unblocked due to a pumping operation of the piezo element 18, leading to an over-spraying or a misprint.
To overcome the problems described above, several conventional methods of making the nozzle have a high hydrophobicity are known.
FIG. 5 shows a drop 3 of the printing ink on the metal plate 1. As shown in FIG. 5, the metal is considered to have a high hydrophobicity when a wet angle xcex8 of ink drop 3 is greater than 45xc2x0. Metals having high hydrophobicity include Ti, Cu, and Au. As shown in FIG. 6, to prevent dregs of the printing ink from clogging the nozzles 12 of the print head 10, a process of either of depositing or coating a metal having a high hydrophobicity such as Ti, Cu and Au is additionally performed.
In another conventional approach, as shown in FIG. 7, first the print head 10a is located on a stage plate 21 and is secured by a head holder 25. Then, a fluorine-based polymer such as Cytop(trademark) or Teflon is applied to the nozzle 12 while rotating print head 10a about a rotation axis 23, so that the nozzle 12 has a high hydrophobicity.
However, in the case of depositing or coating a metal having a high hydrophobicity, the metal coating film may be easily exfoliated so that the nozzle undesirably has a high hydrophilicity. Further, in the case of applying a hydrophobic material, i.e., a fluorine-base polymer to the nozzle, the nozzle of the print head may be clogged because the hydrophobic material has an inherent viscosity.
An object of the present invention is to provide a print head of an inkjet printer which has nozzles having a high hydrophobicity, and a method of manufacturing the same.
In order to achieve the above object, an inkjet print head includes a nozzle, an ink pool temporarily holding printing ink and a first screen. The first screen has at least a convex bar column, the bar column having a plurality of spaced apart bars arranged in a longitudinal direction of the ink pool. A piezo element pumps the printing ink from the ink pool to the nozzle.
A distance between the respective convex bars is about 25 to 30 xcexcm. The present invention further includes a second screen having a plurality of spaced apart convex bars and a channel communicating with both the nozzle and the piezo element.
The channel becomes narrower in width in a direction away from the piezo element.
The present invention further provides a method of manufacturing an inkjet print head having a nozzle plate with a plurality of nozzles. The method includes depositing an amorphous silicon layer on the nozzle plate. The amorphous silicon layer is deposited on the nozzle plate using one of chemical vapor deposition (CVD) technique, sputtering, and physical vapor deposition (PVD).
The method according to the present invention also includes heating a petroleum-based material in a heater, and coating the vaporized petroleum-based material on the nozzle plate of the print head.
The petroleum-based material is heated using an electric furnace or inflammable fuel. The petroleum-based material is, for example, a paraffin wax.